For nearly a century, scientists have struggled with the efficient dehydration of multihydric alcohol compounds. For example, the dehydration of glycerol to acrolein, acetol, and glycerol oligomers was first reported by Nef in 1904. When compositions were heated to temperatures between 430° C. and 450° C., carbonaceous materials and a distillate were produced that contained acrolein, acetol, water, and formaldehyde among other products. Over the next 100 years, occasional reports of catalyzed conversions of glycerol had been communicated targeting conversion to acrolein and acetol directly. As an example, the condensation of glycerol to di-, tri-, and oligoglycerol ethers had been effected with basic catalysts. However, when acidic catalysts were employed, acrolein is formed as a major by-product. As another example, acrolein has also been reported as a product of castor oil hydrolysis and cracking. Conversion of multihydric alcohol compounds has been performed in the temperature range of 250° C. to 400° C., utilizing phosphate or sulfate acid or acid salt as a catalyst. However, clays, zeolites, CO2 or autoionization of supercritical H2O has been shown to effect dehydration with the yields of acrolein rarely exceeding 70%.
While examples of glycerol to acrolein transformation do exist, they are relatively few in number. As recently as 1994, U.S., Japanese, and European patents have been awarded describing the conversion of glycerol to acrolein and acrolein hydrogenation to a mixture of isomeric propanediols. In 1998, platinum bisphosphine complexes were used in the presence of strong acids and syn gas to carry out the conversion of glycerol to acrolein in 80% yield. More recently, glycerol dehydration in subcritical water catalyzed by ZnSO4 in a staged reactor process has been utilized to convert glycerol to acrolein and acrylic acid. To date, processes having high selectivity and commercial viability are still not known for the conversion of glycerol to acrolein.